Users can edit the xml files directly to change the variable
values. However, modification of variables in the xml scripts is best
done using the xmlchange script in the $CASEROOT
directory since it performs variable error checking as part of
changing values in the xml files. To invoke the xmlchange script:

Note: If you want a single quotation mark ("'", also called an
apostrophe) to appear in the string provided by the -val option,
you must specify it as "&apos;".

-silent

Turns on silent mode. Only fatal messages will be issued.

-verbose

Echoes all settings made by configure.

-help

Print usage info to STDOUT.

-warn

Warn and abort if you would be overwriting a current value in the field. This
is useful so you make sure you aren't overwriting a field that is currently set.

-append

Append the given value to the end of the current value of the field. Sometimes you
want to add an option to the end of an existing field, making sure you leave the
current value there (such as adding additional options to the CAM_CONFIG_OPTS
variable).